Field of the Invention
It relates more particularly to an ophthalmic lens comprising means for reducing both ultraviolet light and blue light, in particular phototoxic blue light arriving on the retina of a wearer of spectacles equipped with lenses of this type.
Throughout the present patent application, it will be referred to value ranges, in particular to ranges of wavelengths and angles of incidence. As used herein, “ranging from x to y” means “within the range from x to y”, both limits x and y being included within this range.
As is conventionally the case, the main face of the lens furthest from the eye of a wearer is designated the front face and, in contrast, the main face of the lens closest the eye of the wearer is designated the back face.
Light that is visible to humans extends over a light spectrum ranging from a 380 nanometers (nm) wavelength to a 780 nm wavelength approximately. The part of this spectrum, ranging from around 380 nm to around 500 nm, corresponds to a high-energy, essentially blue light.
Ultraviolet (UV) light is the portion of the luminous spectrum below 380 nm and ranging up to 100 nm. The UVB corresponds to the range from 280 nm to 320 nm and the UVA to the range from 320 to 380 nm.
Description of the Related Art
Many studies (see for example Kitchel E., “The effects of blue light on ocular health>>, Journal of Visual Impairment and Blindness Vol. 94, No. 6, 2000 or Glazer-Hockstein and al., Retina, Vol. 26, No. 1. pp. 1-4, 2006) suggest that blue light has phototoxic effects on the eye, and especially on the retina.
Indeed, ocular photobiology studies (Algvere P. V. and al., “Age-Related Maculopathy and the Impact of the Blue Light Hazard>>, Acta Ophthalmo. Scand., Vol. 84, pp. 4-15, 2006) and clinical trials (Tomany S. C. and al., “Sunlight and the 10-Year Incidence of Age-Related Maculopathy. The Beaver Dam Eye Study>>, Arch Ophthalmol., Vol. 122. pp. 750-757, 2004) demonstrated that an excessively prolonged or intense exposure to blue light may induce severe ophthalmic diseases such as age-related macular degeneration (ARMD).
However, part of this blue light, with a wavelength ranging from 465 nm to 495 nm approximately, promotes health since it is implicated in mechanisms for regulating biorhythms, referred to as “circadian cycles”.
Thus, it is recommended to limit the exposure to potentially harmful blue light, in particular as regards the wavelength band which presents an increased risk (see especially Table B1, ISO 8980-3 standard:2003 (E) with reference to the B(λ) blue light hazard function).
To that end, it may be advisable to wear in front of each of both eyes an ophthalmic lens which prevents or limits the phototoxic blue light transmission to the retina.
It has already been suggested, for example in the patent application WO 2008/024414, to cut at least partially, the troublesome part of the blue light spectrum from 400 nm to 460 nm, by means of lenses comprising a film partially inhibiting the light in the suitable wavelength range, through absorption or through reflection.
Filters cutting off blue light are also described in patent U.S. Pat. No. 8,360,574.
It is furthermore necessary to eliminate as much as possible the harmful influence of ultraviolet light (UV light) on the eye of a wearer of the lens.
Moreover, the person skilled in the art is seeking filters which make it possible to minimize the amount of harmful blue light received by the retina, while preserving the ability to efficiently transmit the visible light at wavelengths higher than 465 nm, on the one hand so as to maintain good vision for the wearer and, on the other hand, not to alter the circadian cycles.
The difficulty lies in the fact that 420 nm to 450 nm wavelength ranges, that are to be filtered, are very close to the wavelength ranges which should not be filtered, or very little.